ORLANDO — As veterans gather together to celebrate each other and compete in the 2nd Annual Invictus Games in Florida, their service dogs are still at their sides helping them to the finish line. The truth is, some of these heroic individuals may not even be alive anymore had it not been for their service dogs.

Although many of these service dogs will go unnoticed, they are there to help their owners with PTSD, diabetes, seizures and depression.

Air Force Sergeant August O’Neill lost his leg in a pararescue in Afghanistan. Along with learning how to live life minus one leg, he battled deep depression. Knowing he needed help, he was accepted to the service dog program and was paired up with Kai a short while later.

Not only does Kai help cheer O’Neill up with he is hit with depression, Kai acts as a physical support system for O’Neill when he needs to balance.

“He does bracing — if my leg gets fatigued, he’ll lean up against me,” O’Neill told ABC News.”He’s my best friend. He’s been with me through the toughest times, and the best times.”

O’Neill recently won the Volleyball semi-finals and is hoping to win so he can share his medal with Kai.

Jesse Graham is a U.S. Air Force veteran crew chief who was left partial paralyzed after a snowboarding accident in 2014. By his side sits Stanley, an English Labrador.

Stanley can fetch items, open and close doors, and even help Graham balance by leaning on him. He also helps Graham get around as fast as possible – especially at the airport.

“He can pull me. He just gets beside me, I grab onto the vest — and we go for a ride,” Graham told ESPN. “There are times he goes really fast. The amount of energy I give him is the amount of energy he gives me. If I get him amped up, we go fast. We fly through airports. It’s great.”

Retired Special Operations Command Sergeant Leonard Anderson and his dog, Azza, were struck by an IED while on patrol in Afghanistan. Azza shielded his body as they wheeled him away on a stretcher. She valued his life over her own.